Accessing elements outside slice using [:]

[Pyrode]

Hey,

The following code allows elements outside the length of the slice to be accessed.

Is this the expected behaviour or a bug?

Thanks

```

package main

import "fmt"

func main() {
foo([]int{1, 2, 3, 4}[0:1])
}

func foo(bar []int) {
fmt.Println(len(bar)) // Output: 1
fmt.Println(bar[0:3]) // Output: [1,2,3]
}

```

[Sean Liao]

https://go.dev/ref/spec#Slice_expressions

> For slices, the upper index bound is the slice capacity cap(a) rather than the length.

- sean

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[Reto]

On Fri, Jan 24, 2025 at 11:57:14PM -0800, Pyrode wrote:
> The following code <https://go.dev/play/p/P2gPMHKuJW8> allows elements

> outside the length of the slice to be accessed.
> Is this the expected behaviour or a bug?

This is expected.
They still share the same underlying data array after all.

https://go.dev/blog/slices-intro might be insightful for you.

If you want to prevent that, return a copy or truncate the cap.
slices.Clip / slices.Clone are helpful there, depending on what
constraints you need.

[Pyrode]

Got it 👍

Thanks for the response!